1. Field of the Invention
The present invention relates generally to the field of orthodontic appliances. More specifically, the present invention discloses a method and apparatus of orthodontic treatment in which any of a variety of orthodontic aligner auxiliaries can be used in conjunction with a removable aligner for orthodontic treatment.
2. Statement of the Problem
In the field of orthodontics, treatment is currently accomplished through the use of a wide range of hardware options available to the practitioner. Taken to a simplest form, these options can be categorized into two groups. The first group is conventional braces, which are based on tooth-mounted mechanical systems intended to reposition a patient""s teeth. The other group includes various types of orthopedic appliances that act to elicit a more physiological or skeletal response. The orthopedic approach is directed not only to repositioning of an orthodontic patient""s teeth, but also to attaining a corrected and stable balance between the jaws, the facial musculature and the bony structures of the face. In practice, orthodontic correction is typically accomplished through a combination of these two approaches where first a patient""s skeletal relationships will be brought into a more harmonious and corrected balance, and once corrected in that manner, the teeth will then be moved into desired final aesthetic positions and desired relationships using conventional braces.
Many auxiliary treatment systems have been developed that generally serve to augment or support the two basic approaches described above. Such auxiliary systems include devices known as retainers, face bows, holding arches, reverse-pull headgear, transpalatal arches, rapid palatal expanders, lingual arch developers, mandibular advancers, lip bumpers and the like. In most cases, such auxiliary treatment devices serve progressively during specific sub-phases of treatment and serve to expedite one treatment objective that must be accomplished before another can begin.
As the science of orthodontic treatment and the related armamentarium has matured, some particularly skilled orthodontists have become so adept at using such auxiliary support systems that their use has been expanded to become a central means of a complete treatment methodology. Many such auxiliary support systems have been commercialized and thus provide the orthodontic profession with many treatment tools, methods and options usefully bolstering treatment methods using conventional xe2x80x9cbracesxe2x80x9d and the orthopedic approaches.
One such orthodontic auxiliary support system to which the present invention is directed is broadly known in orthodontics as the orthodontic tooth positioner. Orthodontic tooth positioners can be characterized as being generally U-shaped, conforming to the shape of the dental arches and formed of a soft, flexible or resilient material. A trough is formed along the generally U-shaped configuration of a tooth positioner, which consists of multiple depressions, each depression being negatively formed to intimately contact and positively accept a corresponding tooth. When placed in the patient""s mouth, a tooth positioner typically spans and intimately accepts all of the teeth of an upper or lower arch of a patient and in doing so typically covers the entire crown of the teeth. Tooth positioners usually do not extend beyond the gingival margin of the teeth and therefore do not typically contact the adjacent soft tissue or the gums.
Generally speaking, positioners used in the past tended to be integral, i.e. formed from a single mass of natural vulcanized rubber material containing two troughs; one of which is upwardly facing for engaging the upper teeth and the other oriented downward for engaging the lower teeth. More recently, tooth positioners are more commonly formed as a set of two separate positioners, with one of a set being adapted to the upper arch and the other independently adapted to the lower arch. Other types of special-purpose positioners are sometimes formed to engage just on side or one quadrant of an arch.
The orthodontic tooth positioner, and methods for forming them were first disclosed in the orthodontic literature in 1946 by H. D. Kesling, a well-known and influential orthodontist of that day. Based on the work of Kesling, positioner-based therapy methods were developed and commercial support for those doctors using positioners was provided by orthodontic laboratories. Kesling published a number of articles extolling the virtues of tooth positioners, describing them as providing effective functional tooth-moving forces without any interference from bands, brackets or wires.
As stated above, both today and in the past, orthodontists choosing to treat patients with tooth positioners typically rely on the services of an orthodontic laboratory to form positioners for their patients. Orthodontic laboratories provide service for the custom-fabrication of a tooth positioner for an individual patient according to a treatment plan and a prescription provided by the attending orthodontist or dentist. For this process, a poured and cured stone replica of a patient""s initial malocclusion is provided by the doctor for the laboratory""s use.
The dental technicians within a laboratory first modify the stone model by cutting the mal-positioned teeth free of the model and the adjacent teeth. Next, a technician repositions the teeth on the model semi-rigidly into desired, ideal positions as specified by the doctor and as determined by the doctor""s diagnosis and subsequent treatment plan. After the stone model has been modified or xe2x80x9ccorrectedxe2x80x9d in this manner, the model will be positioned within a tooth positioner-forming machine where through the simultaneous use of air pressure, vacuum and heat, a sheet of thermo-formable vinyl or other rubber-like or thermo-formable elastomeric material is xe2x80x9csucked-downxe2x80x9d over the stone model(s). After forming the positioner in this manner, excess material is trimmed from the positioner, and it is sent back to the orthodontist""s practice and an appointment is scheduled to seat the positioner in the mouth of the patient.
In the past, the process of forming a tooth positioner has been much more labor intensive. Rather than xe2x80x9csucking downxe2x80x9d a sheet of thermo-formable material, it was necessary to first create a mold and then cast thermosetting materials or other materials that required heat, pressure and time to cure.
As can be appreciated, a completed laboratory-produced tooth positioner reflects the teeth in improved positions and orientations compared to the actual positions and orientations of the teeth at the beginning of a patient""s treatment. When a new positioner is first placed on the patient""s mal-occluded teeth, each tooth will tend to distort and load the elastomeric material adjacent to each tooth impression formed in the positioner. With the positioner fully seated on the patient""s arches, the material adjacent to each tooth will become elastically loaded, and within the elastomeric material of the positioner, energy will have been stored. Essentially, it is the slow dissipation of that stored energy, over time, that provides the gentle, continuous biologically effective force to which the bone underlying the tooth will respond, and the tooth will move into positions according to the gentle urging of the positioner.
As described, positioner-based treatment as first introduced by Kesling in the late 1940""s. The positioners as taught by Kesling were based on relatively inelastic and relatively hard natural rubber materials of the day and therefore such positioners exhibited insufficient elasticity to accomplish primary tooth moving objectives. Such appliances were generally limited to effecting minor tooth movement near the end of treatment and for a period of time they could also be used as a post-treatment retainer of sorts. In order for the tooth positioners used by Kesling to serve as the primary tooth moving treatment modality, the laboratory step involving the physical repositioning of the xe2x80x9cstonexe2x80x9d teeth by the technician had to done in multiple, incremental steps, and multiple, incremental positioners were required. Each incremental step represented only partial movement toward ideal tooth positions. In addition to the constraints of requiring extensive coordination between the doctor and the laboratory, laboratory processing of the early positioners required a time consuming sequence of casting and heat curing. The total cost involved with such a complex process was acknowledged by Kesling as being prohibitive. As Kesling understood, the degree or extent to which a single tooth positioner can be used as the primary method for orthodontic treatment is dependent on the mechanical properties of the material from which the positioner is formed. Kesling lamented the limitations of his positioners but predicted that in the future, through use of then undeveloped materials, tooth positioner based therapy would hold great potential for serving as a primary treatment means.
Driven by both the potential and the limitations of tooth positioners, various substitutes for hard natural rubber were investigated by research groups as well as clinicians wishing to advance the tooth positioner-based treatment philosophy. In the United States, during the 1970""s Cottingham, Warunek, Strychalski and Cunat all investigated medical grade polydimethyl silicate, a material known generically as silicone rubber or silicone elastomer. In Japan, Nishiyama, Kamada, and Horiuchi investigated dimethylvinyl siloxy polydimethylsiloane with a chloroplatinic acid catalyst, generically known as LTV vinyl silicone. Another Japanese researcher; Osama Yoshii developed a tooth positioner treatment methodology using the controlled variable durometer characteristic of LTV vinyl silicone and thus formed progressive positioners based on incremental increases in hardness of a series. Being generally transparent, non-staining, and hygroscopic, the engineered elastomers developed by these investigators solved some of the problems associated with Kesling""s original tooth positioner. To a greater degree, tooth positioners formed from these new materials could be counted on as a dependable means for correcting orthodontic malocclusions. These softer, more resilient materials served in the mouth without discomfort, but still required extensive laboratory casting processes to form them. Nonetheless, as a result of the research described above, a group of elastomeric material systems are currently available for use in forming clear, highly elastic tooth positioners as well as a number of other common orthodontic appliances.
Generally, tooth positioners are popular with young, and perhaps self-conscious orthodontic patients in that they have attributes that reduce social or self-image concerns associated with their appearance during treatment. One fundamental attribute of tooth positioners is that they are removable by the patient, and since in some cases orthodontists prescribe that positioners be worn only after school and during sleep, teenage orthodontic patients have the option of removing their appliances. This allows teenage, as well as adults to avoid speech problems and personal appearance concerns that are commonly associated with conventional braces.
Beginning generally in the early 1980""s, a general increased awareness of the advantages of tooth positioners by orthodontists again drove increased interest. The orthodontic community also noted the commercial success of both the laboratories that produced tooth positioners and the manufacturers and distributors who provided the catalyzable materials as well as the popularity of such appliances with patients. In particular, orthodontists realized that the original vision of Kesling, who first articulated the many potential advantages of positioner therapy, had been to a degree realized through the use of the more resilient modern materials.
Tooth positioners and tooth positioner-based orthodontic therapy evolved into its current status through the use of yet other new materials and new, simpler and less labor-intensive means of forming tooth positioners. As described above, the use of thin sheets of various thermo-formable plastics including vinyl and olefin-type materials has been adopted for current tooth positioners. This, along with an efficient forming process involving the rapid use of pressure, vacuum and heat, has replaced the prior molding and casting processes. Polypropylene in particular exhibits an ideal combination of properties. Particularly in its higher molecular density ranges, polypropylene exhibits desirable mechanical properties in that it is nearly transparent, and in the mouth it is non-reactive chemically and thoroughly biocompatible. One commercial source for the new positioner material is Raintree Essix, New Orleans, La. The use of these materials, including polypropylene in sheet form and in thicknesses of about 1 mm (before thermoforming), eliminates the time-consuming steps of mixing, catalyzing and curing (in some cases heat-curing in a pressure flask) as was required by the outmoded natural rubber, medical-grade urethane, silicone and vinyl silicone series materials. Being thermo-formable, positioners can be easily xe2x80x9csucked downxe2x80x9d over the patient""s reset stone model using heat, pressure and vacuum simultaneously. Since the processing of the new type of thin positioner is so markedly simplified, some orthodontists have even found it practical to form them directly in the orthodontic office, thus avoiding the cost, time and administrative tasks required by laboratory processing. To distinguish between the older types of positioners formed from medical-grade urethane, silicone or vinyl silicone materials, current thin, thermo-formed positioners are generally referred to as xe2x80x9caligners.xe2x80x9d
Once formed, aligners are typically trimmed to closely match the gingival margins of the teeth. When in position in a patient""s mouth, current aligners are virtually invisible, and unnoticeable. Being thin, they do not appreciably interfere with speech as the older, much more bulky urethane, silicone and vinyl silicone-formed versions tended to do. Because of the combined advantages sited previously for tooth positioners combined with the thin, non-bulky, low profile afforded by aligners, aligners are even more readily tolerated by patients and are currently popular with orthodontists.
To demonstrate the general integration and importance of aligner-based treatment methods in the orthodontic field, a combination of current aligner-based therapy philosophies and digital imaging/computer-driven rapid prototyping methods have resulted in the emergence of a significant commercial development described by U.S. Pat. No. 5,975,893 (Chishti et al.). A methodology is taught by Chishti et al. in which multiple aligners are formed for a patient and each upper and lower set of aligners is worn for a set period of time (e.g., about two weeks). Progressive sets of aligners are provided in which each set more aggressively biases a patient""s teeth toward an ideal occlusion. Orthodontic patients undergoing such progressive treatment may typically wear from between 15 to 25 sets of progressive aligners. Over a period of time, the sequential and progressively biased positioners move teeth from their initial maloccluded positions to a near finished and corrected state. This progressive aligner-based program is commercially offered to the orthodontic professional and is also marketed directly to the public by Align Technologies of Sunnyvale Calif. under the name xe2x80x9cInvisalign.xe2x80x9d The Invisalign(copyright) program is promoted as xe2x80x9cinvisible bracesxe2x80x9d and as being a clear alternative to conventional braces.
Aligners, and the commercial fabrication of them is not limited to Align Technologies. Most orthodontic laboratories routinely form aligners according to prescriptions provided by orthodontists. Aligners also continue to be formed within the orthodontic offices. Even though not part of a progressive system such as the Invisalign(copyright) program, such laboratory or in-office-produced aligners perform a wide range of useful treatment functions including correction and retention. For those doctors opting to form their own aligners, methodologies taught by U.S. Pat. No. 5,692,894 (Schwartz et al.) provide one chair-side means of modifying previously formed aligners as may be required by the needs of any one patient.
U.S. Pat. No. 6,293,790, by the present inventor likewise provides a chair-side system of heated pliers useful for activating aligners as required as a patient""s treatment progresses. The heated pliers exploit the thermoformable characteristic of the aligner material and permit them to be locally modified or activated.
Aligner-based therapy is an important and popular treatment modality used in orthodontics today. However, even though commercially successful, aligners still fall somewhat short of Kesling""s original vision of being capable of fully treating the majority of patients presenting for orthodontic treatment. These remaining limitations can be seen for example in the fact that cases acceptable for the Invisalign(copyright) program must fall within the minor to moderate category in terms of severity of the malocclusion in order for aligners of the Invisalign(copyright) program to be effective. Patients exhibiting significant crowding, deep or open bites or excessively narrow occlusions present problems that are beyond the correction capabilities of present aligners. Because of this, for the majority of cases, aligners are still used in conjunction with conventional braces, or used at the end of treatment to accomplish a final aesthetic positioning of the teeth.
As can be appreciated, an individual tooth received within an intimately contacting, but desirably-biased recess or cavity formed within the polymeric shell of an aligner is urged to move in an orthodontically desirable net-vector direction by the slight positional biasing of the cavity. As previously described, as the aligner is positioned on any particular tooth, the difference between the position of the actual tooth, and the repositioned cavity of the aligner tends to load the polymeric shell material in regions just adjacent to the cavity. The stored energy thus imparted into the elastomeric material of the aligner slowly dissipates over time as the bone underlying the tooth physiologically responds to such therapeutic forces. The various corrective, therapeutic forces that are translated to the tooth in this manner can be characterized as: tipping the tooth in terms of torque; tipping the tooth in terms of angulation; rotating the tooth about its central axis; as well as subtle intrusive and in some cases, extrusive forces. Depending on the objectives of the treatment, some teeth may be expected to move bodily through the underlying bone and the gums into completely new locations along a patient""s arches.
When treating a patient""s teeth using an aligner, the effectiveness or intensity of these therapeutic forces decreases as treatment progresses. For instance, as treatment progresses the teeth will comply with the aligner and move as directed. After a tooth has moved to any significant degree toward its desired position, the energy stored within the resilient elastomeric shell of a conventional aligner will be correspondingly reduced and partially spent. Stated differently, as the aligner accomplishes its function of moving the teeth, the forces that it is capable of exerting on the teeth may drop off rapidly. During conventional aligner therapy, when treatment progresses to the point at which the aligner can no longer generate a sufficient level of therapeutic force that is above a minimum physiological threshold needed for tooth movement, the teeth will simply stop moving. For several reasons, such a situation is very undesirable. Traditionally, at such a point in treatment, a practitioner must arrange to have a new aligner formed, either within his office or by a support laboratory. In either case, the forming of a new aligner requires that impressions of the patient""s teeth be taken again, and a new stone model made from the impressions, all of which involve attendant delay and expense. From the patient""s point of view, this typically involves the inconvenience and expense of a separate appointment.
3. Solution to the Problem
In contrast to the prior art discussed above, the present invention employs orthodontic aligner auxiliaries that can be secured to openings in an aligner or other removable appliance to exert therapeutic forces on selected teeth. This enables aligners to used in treatment a much wider range of orthodontic cases and in treatment of orthodontic cases that are more severe. In addition, the orthodontic aligner auxiliaries can be removable or adjustable. This enables the therapeutic forces to be maintained, progressively changed, or reactivated over the course of treatment to significantly expand the capabilities of current aligner-based therapy and address the limitations discussed above.
This invention provides a method and apparatus for orthodontic treatment employing a removable aligner having a polymeric shell with a plurality of cavities shaped to receive teeth. A number of openings are formed that extend through the shell of the aligner into a cavity. An orthodontic aligner auxiliary can then be secured to the opening in the shell of the aligner to exert a therapeutic force on a tooth.
These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings.